The present invention relates to a microwave integrated circuit (MIC) frequency converter and, more particularly, to an image reflection type MIC frequency converter which is low in conversion loss and excellent in frequency characteristics.
In a prior art frequency converter or mixer of the present type, an input signal is fed through a bandpass filter and a transmission line having a predetermined electrical length to a junction. A local oscillator signal is fed through a similar bandpass filter and transmission line to the junction. A diode which is short circuited at one end is connected at its other end to the junction. The junction is also connected through a low pass filter to an output terminal at which the output in the form of an intermediate frequency appears.
In these types of converters, since the signal and local oscillator impedances are matched to the diode by the transmission lines for the input signal and local oscillator signal, respectively, it is difficult or impossible to optimally terminate an image frequency in such a manner as to provide minimum conversion loss.